\documentclass[border=2mm]{standalone}
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{
tick label style = {font=\sansmath\sffamily}, compat=newest}

\begin{document}

\begin{tikzpicture}
\begin{axis}[axis lines=left, enlargelimits=upper, domain=0:2, legend pos=outer north east, width=9cm, height=3.5cm, legend entries = {$y=\sin(2 \pi t)+0.75$,$y=\sin(2 \pi t)+0.25$,$y=\cos(2 \pi t)-0.25$,$y=\cos(2 \pi t)-0.75$}, xlabel=$t$, ylabel=$y$]
\addplot [smooth, color=cyan, line width = 1.5] {sin(deg(2*pi*x))+0.75};
\addplot [smooth, color=blue, line width = 1.5] {sin(deg(2*pi*x))+0.25}; 
\addplot [smooth, color=red, line width = 1.5] {cos(deg(2*pi*x))-0.25}; 
\addplot [smooth, color=orange, line width = 1.5] {cos(deg(2*pi*x))-0.75};
\end{axis}
\end{tikzpicture}

\end{document}